The Dark Knight takes on the movie pirates

The Dark Knight, the latest Batman movie, is clearly a monster hit. The film could even end up besting all-time box office champ Titanic, which took a total of $600.8m. The question is why? Some believe the untimely death of Heath Ledger, who plays the Joker, helped excite tremendous interest in the film. Others believe the film's dark themes reflect the bleak economic and political mood of the times.

But there's an even more intriguing possibility - a highly secretive, six-month, multi-million dollar anti-piracy operation launched by Warner Bros. The studio was determined to prevent pirated copies of The Dark Knight from hitting file-sharing services on the internet before its cinema release. Batman's most likely audience - young men - is the demographic most likely to download pirated films.

These days some pirated movies

are available on the internet and street corners across the world weeks before films are released. The major Hollywood studios claim to lose a combined total of over $6bn a year from such piracy. Films can be pirated from copies smuggled out of post-production companies where the film is edited, the sound track is created or by recording preview screenings on camcorders surreptitiously taken into cinemas.

So Warner took a number of unprecedented precautions with The Dark Knight, which had cost them $180 million to make. It recorded the details of anyone who had access to the film. It varied the ways and times it delivered reels of the film to cinemas to confuse potential pirates, and even held one or two reels back until the last moment so that cinemas didn't have a complete movie from which copies could be made. In the weeks leading up to the film's release,